Two patients had an illness characterized by a positive family history, juvenile onset, macular cherry-red spots, myoclonus, generalized convulsions, and cerebellar ataxia. Neither had dementia, gargoyle facies, bone or joint deformities, or visceromegaly. Vacuolated lymphocytes were not seen in the peripheral blood or bone marrow. Specimens from the rectum and vermiform appendix showed Sudan black B-, Sudan III-, and PAS-positive granules within the neurons of the myenteric plexus. On electron microscopic examination, lysosome-like bodies, membranous cytoplasmic bodies, pleomorphic lamellated bodies, dense bodies, and lipofuscin-like bodies in the neurons were seen, with a suggestion of morphological transitional forms among them. Sialoglycopeptides, especially sialic acid, were increased in the urine, but excretion of acid mucopolysaccharides was normal. Assays of lysosomal enzymes in leucocytes showed normal enzymatic activity. On the basis of the clinical, biochemical, and histological results, we suggest that these two cases and four similar cases reported in the literature be classified differently from the previously described lipidoses, although it is not known whether these cases represent a new entity or merely a clinical variant of juvenile lipidosis.